This invention is an improvement on the sustained-release oral drug dosage forms described in U.S. Pat. No. 5,007,790. Those dosage forms consist of a plurality of solid particles composed of a solid drug dispersed in a hydrophilic water-swellable crosslinked polymer. The polymers of the particle imbibe water, causing the particles to swell and the drug contained in the particle to dissolve and leach from the particle. After the drug has leached from the particles, the crosslinks of the polymer cleave to allow the polymer to dissolve.
In contrast to the polymers described in U.S. Pat. No. 5,007,790, the polymers used in the present invention are not crosslinked. They are thus inherently safer in that possible toxicity from any residual crosslinking agent is avoided. In addition, the particles made from the present polymers may be formed into solid bodies (e.g., tablets) by direct compression without binders. Binders had to be added to the polymers of the prior patent in order to compression-mold the particles. This lack of binder makes the dosage forms easier to fabricate and less expensive. Finally, once the particles have been ingested and they imbibe water, they swell to a size which promotes retention, and they become exceptionally soft and slippery. As a consequence of the latter, they tend to resist expulsion from the stomach by the peristaltic motion of the stomach walls better than the particles of the prior patent.
Hydroxyalkylcelluloses have been used commercially as binders for sustained release tablets, and as ingredients in ophthalmic preparations.